DETECTION OF STRAIN AND DAMAGE DISTRIBUTION IN SICF/SIC MECHANICAL TEST COUPONS

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, "damage tolerant" design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high temperature assessment of a SiCf/SiC composite under axial fatigue loading. Data from these separate monitoring techniques plus ancillary use of X-Ray computed tomography and optical inspection were correlated to monitor the onset and progression of damage during cyclic loading.